The experience of having eyes water excessively when sick is known medically as epiphora. This phenomenon occurs because a systemic illness, such as a common cold or the flu, disrupts the delicate balance between the rate at which tears are produced and the rate at which they drain away. The body’s inflammatory response to an infection is the primary driver behind this temporary increase in tear overflow.
The Purpose and Process of Normal Tearing
The lacrimal system is a complex network of glands and ducts that keeps the surface of the eye lubricated and clear. Tears are generated by the lacrimal glands, located above the outer corner of each eye, and are composed of water, salt, and protective substances. These fluids are continuously spread across the eye with every blink, forming a lubricating film that nourishes the cornea and washes away debris.
Tears are produced in two main forms: basal tears and reflex tears. Basal tears are secreted constantly at a slow rate to maintain moisture and function. Reflex tears are produced in much larger volumes—sometimes up to 100 times the basal rate—in response to sudden irritation or injury to the eye surface.
Normally, tears exit the eye through two small openings, called the puncta, located in the inner corner of the upper and lower eyelids. They travel through tiny tubes called canaliculi into the lacrimal sac before flowing down the nasolacrimal duct. This duct channels the tears directly into the nasal cavity, which is why excessive tearing often causes a runny nose.
Illness-Related Causes of Excessive Tearing
Illness causes epiphora through a combination of tear overproduction and impaired drainage, both stemming from the body’s inflammatory response. When a viral infection takes hold in the upper respiratory tract, the resulting inflammation creates two distinct problems for the lacrimal system.
One major mechanism involves reflex tearing, where inflammation in the nasal passages triggers a sensory response. The internal irritation caused by congestion and swelling stimulates the trigeminal nerve, a major sensory pathway connecting the nasal cavity and the lacrimal glands. This stimulation signals the lacrimal glands to dramatically increase tear production as a protective measure, flooding the eye’s surface.
The second mechanism is physical blockage of the drainage system. Illnesses like the common cold or sinusitis cause the mucous membranes lining the nose to swell. Since the nasolacrimal duct passes through the bony structure of the face to empty into the nasal cavity, the surrounding swollen tissue can constrict or completely block the duct’s opening.
This congestion prevents tears from draining into the nose at the normal rate. Even if tear production is only slightly elevated, the tears have nowhere to go and subsequently spill over the eyelid onto the cheek.
When to Seek Medical Attention
While temporary excessive tearing is a common symptom of a cold or flu, certain signs suggest a more serious underlying condition. You should contact a healthcare provider if tearing is accompanied by any of the following symptoms:
- Severe, constant eye pain or tenderness around the eye socket or nose.
- A sudden change in vision, such as blurriness or loss of clarity.
- Significant sensitivity to light (photophobia).
- The appearance of thick, colored discharge, such as yellow or green pus, which can indicate a bacterial infection.
- Excessive watering persists long after all other cold or flu symptoms have resolved, suggesting a lingering obstruction.
- Swelling and redness over the lacrimal sac area, near the inner corner of the eye, signaling a possible infection of the tear drainage system.